This invention relates generally to apparatus for monitoring and/or controlling premises from a remote location and, more particularly, to apparatus of that type that utilizes existing telephone lines and equipment to effect the monitoring and control.
There are many occasions when owners of premises, such as homes, summer homes, offices, businesses and the like are absent from their premises for certain periods of time and would like to be assured during those periods that their premises are in a "normal" condition. The "normal" condition may, for example, be one in which the temperature of the premises is within some predetermined range, in which electric power is available, and/or in which no intrusion into the premises has taken place. Numerous other types of conditions may be considered important for monitoring by the absent owner depending upon the nature and contents of the premises and upon the owner's subjective desires.
It has been recognized that one convenient way of providing this type of supervision is by utilizing existing telephone lines and equipment for reporting purposes. In one system which has been proposed, specially designed auxiliary equipment is installed at the subscriber's premises which is adapted to sense "abnormal" conditions at the premises and to report those conditions by means of automatically dialing a telephone call to an entity which can take action on them. The entity might be the fire department in the case where the abnormal condition is an excessively high temperature or excessive smoke, the police department in the case where the abnormal condition is an intrusion, or the owner's answering service in the case where the abnormal condition corresponds to some other, less urgent type of problem.
The auxiliary equipment installed at the subscriber's premises in systems of this type is generally rather complex and expensive. The equipment not only has to be capable of sensing abnormalities at the premises, but also has to be capable of automatically dialing the appropriate entity to be informed and of sensing when the alarm-reporting call has been completed.
Supervisory systems have also been proposed which operate under the control of the telephone company central office equipment serving the subscriber. Generally, in systems of the latter type, special equipment must be installed both at the subscriber's premises and at the central office. In one system of this type, a special short-duration control signal is transmitted from the central office to each subscriber participating in the supervisory service. The control signal forces the special equipment at the subscriber's premises to go off-hook for a short period of time and to report on the conditions at the premises. The transmitted control signals must be of short duration because the central office must perform a rapid scan over many subscribers in order to insure reasonably short time intervals between the successive checks at each monitored location.
In another central office involving system, which system is disclosed in my co-pending patent application filed on even data herewith and entitled "Remote Supervisory System", Ser. No. 926,102, special auxiliary equipment at the subscriber's premises creates a temporary off-hook condition on the subscriber's line. During the temporary off-hook condition, the equipment transmits status reporting signals to the central office and keeps on repeating the off-hook condition and the signaling until the equipment is "reset" or has timed-out automatically. The central office linefinding equipment identifies the subscriber as it does in the case of a normal outgoing call and receives the status reporting signals. The subscriber's identity and information concerning the status of his premises are forwarded by the central office to an entity which can take corrective action.
The last two systems require equipment and/or programming modifications to the central office with which they operate. Thus, the supervisory service becomes available to the subscriber only after the telephone company servicing his area decides to incorporate the necessary changes into the central office.
A further disadvantage of all three of the above-discussed systems is that they typically report only after conditions at the premises have become abnormal. There is no way for the absent subscriber to assure himself, at any time he so desires, that conditions at his premises are in fact "normal". When the subscriber desires a status report, he may be located anywhere, including overseas. It would be highly desirable if the owner could receive the status report simply by placing a normal telephone call through the telephone network to his vacant premises. It would also be desirable if such a service could be provided without the need for modifying the telephone central office or other equipment.
Another function which an owner often desires to perform while absent from his premises is to control certain operations there. The absent owner may, for example, want to activate lights, appliances or other devices, change a thermostat setting or perform other such functions prior to his return. It would also be desirable if apparatus were available which enabled an owner to perform such functions simply by placing telephone calls to his vacant premises.